世界电力牵引的发展已有近百年历史了。电力牵引的优越性越来越显著。许多国家在运输最繁忙的主要干线采用电力牵引,大幅度地提高了运输能力。早期铁路电气化主要是直流和单相低频交流制。自从本世纪五十年代初法国首先采用25kV 单相交流工频电流制以来,世界各国铁路电气化优先采用这一制式。我国也采用了这种先进的电流制。电力机 The development of electric traction in the world has been nearly a century old. The superiority of electric traction is more and more obvious. In many countries, the use of electric traction on the busiest trunk lines has greatly increased transport capacity. Electrification of the early rail is mainly DC and single-phase low frequency AC system. Since the early fifties of this century, France first adopted 25kV single-phase AC power frequency current system, the world’s railway electrification priority to adopt this system. Our country also adopted this advanced current system. Power machine